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Summary
  • The alternator converts mechanical energy into electrical energy via magnetic induction. This charges the battery while the engine is running.
  • Alternators don’t blow without any reason. Make sure to have a trained professional inspect your vehicle for any underlying issues once this happens.
  • A blown alternator fuse can cause your vehicle to exhibit several symptoms, such as a dead battery, dim lights, illuminated warning lights, and other electrical oddities.
  • A new alternator fuse can cost around $20 for the part itself, but you can expect the price to go up or down, depending on your vehicle’s specifications.

Your car contains a wide range of fuses, including fuses for the alternator. The primary alternator fuse (or fusible link) will blow whenever there’s excessive current flow due to a short circuit or other malfunction.

When the primary alternator fuse blows, the charging system will no longer work as it should—and you’ll begin to notice a variety of problems.

placement of the car megafuse
The schematic is a generic illustration of the placement of the megafuse. Different platforms are wired slightly differently than the one shown. |  Image Source: Richard McCuistian

As you might know, the alternator charges the battery and supplies electricity to the vehicle whenever the engine is running. The alternator is driven off the engine by a belt, which allows the alternator to convert mechanical energy into electrical energy through magnetic induction.

Most of the time, there’s a high-amperage fuse or fusible link between the alternator’s battery terminal and the battery. Also, there are usually low-amperage fuses in series with the alternator’s sense terminal and ignition terminal.

What Is an Alternator Fuse?

But when someone mentions the “alternator fuse”, they’re generally referring to the primary, high-amperage fuse (or fusible link) between the alternator and the battery.

Like any fuse, the primary alternator fuse acts as a circuit protection device. When there’s excessive current flow, the fuse blows to prevent a circuit overload that could lead to melted wires, damaged components—and a potential fire.

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Signs of a Bad Alternator Fuse or Fusible Link

It’s important to point out that alternator fuses do NOT blow for no reason. If your car’s alternator fuse is blown, that means there’s a problem you need to address.

The only exception is if the vehicle has been worked on or jump-started recently. Mistakes, such as jump-starting the battery with the cables reversed and grounding the alternator’s battery terminal with a wrench, can cause the fuse to blow.

A blown alternator fuse will prevent the charging system from working properly, leading to a variety of problems that can mimic a bad alternator. Before condemning the fuse, however, you’ll want to perform a thorough diagnosis of the vehicle to verify the cause of the concern.

Common symptoms associated with a blown alternator fuse include:

Dead Battery

As was mentioned earlier, the alternator charges the battery while supplying the rest of the car with electricity. If the alternator’s fuse or fusible link is blown, the alternator will not be able to charge the battery. The battery then doesn’t store enough power for starting the car or keeping it running.

Lighting Issues

You may notice the headlights and other lighting start to dim if the alternator fuse is blown, preventing the charging system from working properly.

Warning Lights

The charging system warning light on the dashboard will likely illuminate if the alternator fuse is blown. A blown alternator fuse can also trigger the check engine light and many other dashboard warnings due to system undercharging.

Other Electrical Oddities

Your car contains an array of electronics, all of which rely on charging system voltage. As such, a blown alternator fuse can cause a myriad of transient electrical issues, especially on modern, computer-controlled vehicles.

car fuse
The primary alternator fuse acts as a circuit protection device. When there’s excessive current flow, the fuse blows to prevent a circuit overload that could lead to melted wires, damaged components—and a potential fire.

How to Tell if an Alternator Fuse is Blown?

Testing an alternator fuse is no different than testing any other type of fuse. First, perform inspect the fuse by checking whether its conductive element is broken. A broken element means the fuse needs replacement.

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If you can’t tell whether the fuse is good just by looking at it, you can use a digital multimeter (DMM) set to ohms to test for continuity. Here’s how to do it:

  • Make sure the vehicle’s ignition switch is turned OFF.
  • Set your digital multimeter (DMM) to the ohms setting.
  • Connect one meter lead to one of the fuse’s terminals. Connect the other meter lead to the other fuse terminal.
  • If your meter reads out of limits, the fuse is bad and needs replacement. A reading of anything other than out of limits (OL) indicates the fuse is intact.

The video below demonstrates testing an alternator fuse with a DMM:

How Do You Change an Alternator Fuse?

How you replace an alternator fuse will depend on its type.

  • Blade-Style Fuses: Pull them up and of their socket.
  • Cartridge-Style Fuses: Pull them up and out of their socket. Some bolt into place, so be careful when removing them.
  • Bolt-Dowel Fuses: Use tools to unbolt them.

In some cases, the primary alternator fuse may actually be a fusible link, which must be cut out of the wiring harness to be replaced.

Remember: No matter what kind of fuse you’re dealing with, you’ll want to disconnect and isolate the negative battery cable prior to replacement.

The video below demonstrates replacing one type of cartridge-style fuse:

Alternator Fuse FAQ

Can a Blown Alternator Fuse Drain the Battery?

Not likely. The fuse serves as a protection device, blowing to keep a circuit overload when there’s too much current flow.

In rare cases, a blown alternator fuse can cause a parasitic drain on the battery when it results in an open circuit.

Is It Dangerous to Drive With a Blown Alternator Fuse?

No, it’s not. You can continue driving while your vehicle has a blown alternator fuse, but that doesn’t mean you can forget about it.

When the alternator fuse blows, it means it prevented a circuit overload that could damage parts and even cause a fire.

With the alternator fuse blown, your circuits won’t have any protection. If another excessive current runs through the connection, it could cause problems for the system.

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How Much Does a Replacement Alternator Fuse Cost?

Replacing an alternator fuse is a DIY-friendly repair that you can usually do yourself. But if you’re unsure what caused the fuse to blow in the first place, you might want to have a professional figure it out.

Alternator fuses generally cost less than $20 for just the part itself. Of course, the exact cost will vary depending on a variety of factors, such as the year, make, and model of your vehicle.

Where is the Alternator Fuse Located?

The fuse is usually under the hood on the driver’s side, but it’s exact location varies depending on the vehicle.

Consult your owner’s manual to determine the location of the alternator fuse on your car.

Replacing Your Vehicle’s Alternator Fuse

A blown alternator fuse or fusible link can make it difficult to start your vehicle. On the bright side, it shouldn’t be too difficult to get a replacement that fits your vehicle with the help of CarParts.com.

The best part? You don’t even have to leave your home to get a replacement. You can use your mobile phone or computer to visit CarParts.com. Browse our catalog and check for fitment with the help of our vehicle selector. Simply input your vehicle’s details, including its exact year, make, model, and engine.

We only source our parts from the most trusted manufacturers in the industry. It’s also worth mentioning that our warehouses are located all over the US, meaning you can receive your order within days.

Browse our collection of high-quality auto parts at CarParts.com.

About The Author
Written By Automotive Subject Matter Expert at CarParts.com

Mia Bevacqua has over 14 years of experience in the auto industry and holds a bachelor’s degree in Advanced Automotive Systems. Certifications include ASE Master Automobile Technician, Master Medium/Heavy Truck Technician, L1, L2, L3, and L4 Advanced Level Specialist. Mia loves fixer-upper oddballs, like her 1987 Cavalier Z-24 and 1998 Astro Van AWD.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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Kim

I was looking for someone to tell me what tool they use to remove the bolt for one type of alternator fuse, but nobody even mentioned it.

Cameron potts

Hello
My 2000 Honda Accord keeps frying brand new.alternators .its.a.3.0 vtec v6 .engine & trans work great .its just this electrical issue with my alternator not Recharging the batt

Tony

Could someone please tell me 2007 Cadillac DTS

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